$ { {5} \times \left[\begin{array}{rrr}{1} & {0} & {-1} \\ {-2} & {1} & {-1}\end{array}\right] = {?} } $
To multiply a matrix by a number, multiply each item of the matrix by the number. ${\left[\begin{array}{rrr}{5}\times{1} & {5}\times{0} & {5}\times{-1} \\ {5}\times{-2} & {5}\times{1} & {5}\times{-1}\end{array}\right]}$ Now, simplify: ${\left[\begin{array}{rrr}{5} & {0} & {-5} \\ {-10} & {5} & {-5}\end{array}\right]}$